One of the largest of its type in the country, the crane began lifting the final 15 beams to finish a low-level bridge spanning Bingley South Bog to, a Site of Special Scientific Interest. The bridge beams weigh up to 36 tonnes each.
Engineers involved in the two-day lifting operation have to work around two major mains water pipes under the bridge.
Paul Gott, of contractor Amec, said: "The aqueducts run across the surface of the bog and they carry some of the mains water supply into Bradford.
"The water in the aqueducts is under pressure and we obviously have to make sure that our work doesn't disrupt the pipes or the water supply in any way.
"The work requires great precision because this is a low-level bridge structure with only a very small amount of clearance above the aqueducts. We will be working very closely throughout the operation with engineers from Yorkshire Water."
The £2.5m bridge has been designed to minimise impact on the ecology of the South Bog site.
Rare wetland plants growing in the path of the new bridge were transplanted to other areas of the bog before work began. Seeds from the plants are also being stored at Sheffield University as a back-up.
Work on the final stages of the scheme's second major bridge structure at Cottingley Viaduct is likely to take place at the end of this week when the final "pour" of over 300 tonnes of concrete will complete the viaduct surface.
The £5.5m Cottingley Viaduct is one of nine bridge structures on the 5km Bingley relief road.
Highways Agency project manager Peter Scally said that, weather conditions permitting, the road is on course for completion this autumn.
Mr Scally said: "The contractors have made good progress so far, despite some very wet weather at the end of last year. We are now moving into the final stages of the scheme and around a third of the blacktop surfacing has already been laid."